1. Field of the Invention
This invention relates to power operated actuators for opening and closing the convertible top of an automobile, and in particular to such an electro-hydraulic rotary actuator.
2. DISCUSSION OF THE PRIOR ART
Power operated systems for opening and closing the convertible top of an automobile are well known. Typically, these systems employ one or more hydraulic cylinders on each side of the frame (known as the top stack) of the convertible top for rotating the bows of the top stack about a lateral pivot axis, which is usually positioned toward the rear of the passenger compartment. Because the motion required of the bows was rotary, but the cylinders only produced linear motion, the mechanism was required to convert the linear motion of the cylinder to the rotary motion required for operating the top, and therefore was relatively complex. Also, because of the stroke required of the cylinders at acceptable force levels, the cylinders were relatively long. These systems also involved relatively complex plumbing and hydraulic control circuits, which added to the cost of the system.
An electro-hydraulically powered rotary actuator has also been proposed for opening and closing the convertible top of an automobile. U.S. Pat. No. 3,359,870 discloses such a system. While eliminating much of the mechanism associated with hydraulic cylinder operated systems, the prior rotary actuator operated systems still required complex plumbing arrangements. For example, these systems required an external reservoir and/or solenoid or manually operated hydraulic valves. Also, since the operator of the automobile usually must latch the top in position after the hydraulic actuator has opened or closed it, it is desirable to provide a hydraulic system which helps the operator latch the top by holding it open or closed during latching. The present invention is aimed at providing such holding in a simple, efficient and economical rotary actuator system.